Large Tortoiseshell Butterfly Declared Resident Species in the UK

The large tortoiseshell butterfly (Nymphalis polychloros), once considered extinct in Britain, has been officially recognized as a resident species following multiple sightings across various regions, including Kent, Sussex, Hampshire, Dorset, Cornwall, and the Isle of Wight. This marks a significant milestone for the UK’s biodiversity, bringing the total number of native butterfly species to 60. Richard Fox, head of science for Butterfly Conservation, expressed optimism about the species' return, noting, “The signs are really positive... It’s not well-established enough yet to say it’s definitely back for good.”

The Guardian

Historically, the large tortoiseshell butterfly thrived in Britain until its extinction in the 1960s, a decline attributed to the loss of elm trees due to Dutch elm disease. However, lepidopterists now suggest that Britain may have always been at the northern limit of the species' natural range. The recent resurgence is believed to be influenced by climate change, which has facilitated the migration of butterflies from continental Europe, particularly from the Netherlands and France. Since 2006-07, the butterfly has been spotted in increasing numbers along the southern coast of England, although some sightings have been linked to unauthorized releases by butterfly breeders.

The Guardian

Since 2020, evidence of large tortoiseshell caterpillars feeding on trees has been documented, indicating that the species is successfully breeding in the wild. The adult butterflies emerge in spring, mate, and lay eggs, with their offspring expected to take flight as adults by midsummer. This breeding cycle raises hopes for a growing population in the coming years.

The Guardian

Butterfly Conservation has added the large tortoiseshell butterfly to its first sightings page and is encouraging the public to report any observations through iRecord, a citizen science app. This initiative aims to enhance understanding of the butterfly's distribution and population dynamics.

The Guardian

While the return of the large tortoiseshell butterfly is celebrated, experts caution that it is still uncertain whether the species will establish a stable population across diverse landscapes in Britain. Richard Fox emphasized the need for continued monitoring, stating, “We’re still in that zone of uncertainty at the moment, but there are exciting signs.”

The Guardian

• “The signs are really positive, which is lovely,” — Richard Fox, Head of Science, Butterfly Conservation

The Guardian

The resurgence of the large tortoiseshell butterfly represents a hopeful development in the conservation of British wildlife, highlighting the potential impacts of climate change on species distribution and the importance of citizen engagement in monitoring biodiversity.

The Guardian